initializing arrays with user input

This is a discussion on initializing arrays with user input within the C Programming forums, part of the General Programming Boards category; My assignment is to ask the user what size array they want. The compiler keeps saying, constant expression required in ...

  1. #1
    Unregistered
    Guest

    Angry initializing arrays with user input

    My assignment is to ask the user what size array they want. The compiler keeps saying, constant expression required in function main().
    code is:
    cout<<"Enter size of array:"<<endl;
    cin>>x;
    int array1[x];

  2. #2
    Code Warrior
    Join Date
    Nov 2001
    Posts
    669
    I think this is not possible. You must define "char string[100];" and then you can enter how many arrays will you use.
    Current projects:
    1) User Interface Development Kit (C++)
    2) HTML SDK (C++)
    3) Classes (C++)
    4) INI Editor (Delphi)

  3. #3
    Banned maes's Avatar
    Join Date
    Aug 2001
    Posts
    744
    the only way for doing this is with dynamic memory allocation( I think).
    Code:
    char *string;
    
    cout<<"Enter size of array:"<<endl; 
    cin>>x; 
    string= (char *) malloc(sizeof(char)*x);
    ...
    ...
    ...
    free(string);//do not forget this, you have to free the memory
    A better way of doing it is with "new" and "delete"
    but I can't give you an example because I only use them 1 or 2.
    look them up and use them instead of malloc
    SVG is the future

  4. #4
    the Corvetter
    Join Date
    Sep 2001
    Posts
    1,584
    You can use realloc. That way, you just realloc after every input.
    1978 Silver Anniversary Corvette

  5. #5
    Linguistic Engineer... doubleanti's Avatar
    Join Date
    Aug 2001
    Location
    CA
    Posts
    2,459
    your compiler might register memory frees as an atexit command... so check...
    hasafraggin shizigishin oppashigger...

  6. #6
    Unregistered
    Guest
    new and delete are C++ operators. This is the C board. also in C you do not need to cast malloc(), in fact it is better if you don't.
    Furthermore, if you have GCC or a C99 compatible compiler you can use you original code.

  7. #7
    Registered User
    Join Date
    Sep 2001
    Posts
    752
    Arrays must know how long they are at compile-time. If you want to allocate a certain amount of memory based on run-time information, you'll have to use dynamic memory allocation...
    Code:
    #include <stdlib.h>
    int main ()
    {
     int N;
     int * a;
     printf("Enter size of array: ");
     scanf ("%d", &N);
     a = malloc (sizeof(int) * size);
     // Now a is an array of N ints.
     return 0;
    }
    I am pretty sure this can be done with C++ arrays however, check their forum.
    Callou collei we'll code the way
    Of prime numbers and pings!

Popular pages Recent additions subscribe to a feed

Similar Threads

  1. How to limit user input to a certain number of digits?
    By NewbGuy in forum C Programming
    Replies: 7
    Last Post: 05-08-2009, 09:57 PM
  2. can someone help me with these errors please code included
    By geekrockergal in forum C Programming
    Replies: 7
    Last Post: 02-10-2009, 01:20 PM
  3. SSH Hacker Activity!! AAHHH!!
    By Kleid-0 in forum A Brief History of Cprogramming.com
    Replies: 15
    Last Post: 03-06-2005, 02:53 PM
  4. Nested Structures - User Input
    By shazg2000 in forum C Programming
    Replies: 2
    Last Post: 01-09-2005, 09:53 AM

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21